The electric guitar is fundamentally an analog instrument, and its electrical design has not changed appreciably over the last 50 years. With the advent of low-cost processing and computers, the ability to provide sophisticated musical interfaces has made exponential progress over the same time period. The advantages that this technology can bring to the music world is well established in the keyboard world, where pianos have been transformed from a purely mechanical instrument into sophisticated music generators capable of sounding like any other instrument. Costs have plummeted to where an electronic keyboard is available as an inexpensive consumer product. The same can not be said to be true in the guitar world.
One of the main reasons that guitars have not entered into the digital world to the extent that pianos have has to with the fact that piano keys can be thought of as switches, and so adapt well to a digital interface. In contrast, an electric guitar relies on the vibration of a metal string across an electromagnetic pickup in order to produce an analog signal.
There are existing guitars that convert this analog signal into a digital form that can then be used to interface to digital processors. The musical instrument digital interface (MIDI) is standard format in musical electronics, and there are a number of MIDI guitars currently available. However, these have some fundamental flaws that prevent the guitars from providing an authentic feel and sound to the musician.
The principal problem is that in order to convert from the analog form to a digital one, the frequency of the string must be determined, which takes some perceptible amount of time. This delay or latency is very distracting to a musician attempting to play the guitar since the audio feedback is delayed from the time the desired note is struck until the sound is heard. The problem gets worse with lower frequencies as the corresponding periods become longer. The fact that the amount of latency varies considerably across the guitar note spectrum is another aspect of this problem that requires adaptation on the part of the player.
In addition to the frequency, a MIDI note event also includes a parameter for velocity or volume. In a keyboard, this represents how fast, or how hard a key was struck. In existing digital guitar methods such as those described above, there are additional problems in accurately determining the volume of the note. There is again a finite time that must elapse before this determination can be made, which can cause additional delays on top of the frequency determination. Since both the frequency and the volume information have to be released together to form a MIDI code, the delay becomes the worst of both.
Both the volume and frequency determination of the note are also prone to many errors, because there are many overtones in a guitar signal that combine to make these processes difficult. For example, ambient noise pickup (typically 60 cycle “hum”) or a variety of other factors may cause false notes.
Another problem with existing digital guitars is capturing certain expression nuances. For example, an important element of playing guitar is note bending, or changing the pitch of a note by stretching the guitar string after it is initially played. Since the pitch of the note is constantly changing, the problem of converting this in real time to a digital signal becomes impractical. Other expression nuances include hammer-ons, pull-offs, and producing vibrato.
In order to accomplish the goal of a digital interface without latency, some systems use the fret board of the guitar as a switch matrix input, similar to a keyboard. Various techniques have been employed to form a switch matrix. One is to actually install a series of push-button switches on the fingerboard. This approach does not use guitar strings and requires a substantial adaptation of playing style, without allowing for the capture of expression nuances.
Another technique that has been used takes advantage of the fact that the guitar strings are metal, and electrically conductive, as are the fret bars located on the guitar neck. As the strings are fretted by the player, a contact is made and can be read. It is necessary in this case to produce special fret bars that are separated into six segments in order to distinguish a unique contact when all strings are fretted across and a common bus is formed. This method is expensive to manufacture and is incapable of capturing expression nuances.
Overview of the Disclosure
To solve these problems, a method that eliminates the need for frequency analysis and analog-to-digital conversion is required.
To that end, a digital guitar is described. According to various embodiments, the guitar eliminates latency problems described above, is cost-effective, does not require adaptation on the part of the musician, and captures the nuances of musical expression necessary to make a digital guitar similar to a normal guitar.
According to some embodiments, a non-contact sensor system that can be embedded into a conventional guitar fingerboard is described. The sensor may be accurate enough to detect a fingertip fretting a string to within a high degree of precision. In some embodiments, the sensor may be calibrated so as to allow for variations in manufacturing, the playing environment, and playing styles. According to certain embodiments, the sensors may be connected to a processing circuit in order to generate a signal indicative of the musician's finger locations.
According to another embodiment, a system is described for determining when a string has been played. In some embodiments, light emitting elements are provided under the strings and an array of photosensitive elements may be placed above the strings. Shadows may be detected to determine the movement or location of the strings. Data may be stored over time to map the locations of the strings and determine picks and/or strums, to determine finger bends, to determine a note volume, and other characteristics according to certain embodiments.
According to yet another embodiment, an alternative system is described for determining when a string has been played. In some embodiments, this system uses existing pickups in an electric guitar and determines when a signal is generated. The system may advantageously determine that one or more strings have been played without latency associated with frequency analysis. In some embodiments a separate pickup is used for each string in order to provide additional confirmation or accuracy. Some embodiments may comprise magnetic pickups, piezoelectric pickups, or a combination of magnetic and piezoelectric pickups.
According to some embodiments, a musical instrument is described that may be used as a game controller. The musical instrument may generate a digital signal that indicates the locations of a users fingers when they are used to play the instrument. The signal may also indicate when one or more strings or simulated strings have been played. The digital signal may be configured to be used by a video game or other computing system with an entertainment or learning application. The musical instrument configured to be used as a game controller may be operable as an instrument independent of an external computing system in some embodiments. For example, a control signal for a game system may be output via a wireless transmitter in an electric guitar and an analog signal may be output via a standard connector to a guitar amplifier.
According to some embodiments, a system is described comprising a playing surface transparent to light having a wavelength in an operating spectrum and at least one sensor module below the playing surface. The at least one sensor module generates and detects light in the operating spectrum, and is configured to detect a finger at a location proximate the playing surface. The sensor module generates a signal indicative of the location of the finger when it is detected.
According to some embodiments, a method is described. The method includes emitting a light from a light source directed generally towards a playing surface of a musical instrument and detecting a first portion of the light with a first receiver module proximate the light source. A second portion of the light is detected with a second receiver module proximate the light source. Based on the first and second portions of the light, it is determined whether a finger is close enough to reliably trigger a musical event.
According to some embodiments, a method is described including emitting a light from a light source towards a playing surface of a musical instrument. A portion of the light that has been diffused by a finger of a user is detected with a receiver module located proximate the light source. It is determined, based on the detected portion of the light, whether the user has activated the musical instrument.
This section is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application.